This invention relates to a rotational control apparatus, such as a pneumatic on/off fan clutch and, more particularly to a dust seal design which serves to limit the exposure of the fan clutch to moisture and other environmental contaminates.
Common cooling systems for use in diesel engines such as over-the-road trucks, off-road equipment and agricultural equipment include a spring-bias or air-engaged on/off fan clutch for selective cooling fan operation. Typically, an on/off fan clutch is mounted to the front of the engine block and the clutch is belt-driven by the crank shaft pulley. Electronic control of such engines is now fairly standard so that, based on a signal from the engine""s electronic control module (ECM), the fan clutch is activated to turn the cooling fan on and off. A typical diesel engine heat exchange (cooling) system includes an on/off fan clutch, a solenoid valve, a cooling fan and a fan shroud, and operates in conjunction with engine coolant, charge air and air conditioning systems. Such heat exchange systems may also be used in conjunction with transmission cooling and hydraulic cooling systems. Fan clutches of this type shown in U.S. Pat. Nos. 3,253,687, 4,425,993, 4,657,126 and 5,704,461 have proven to provide precise power, exceptional economy and dependable, long lived durability.
The operational environment for a fan clutch is an extreme and unfriendly one. The engine and adjacent systems may be operated for long periods of time, in high heat conditions (or even extreme cold conditions). In addition, conditions may be quite dirty, dusty and the system can be exposed to significant amounts of moisture in use. It is therefore quite important to prevent contamination of the operable components of a fan clutch from such adverse atmospheric conditions and contaminants.
U.S. Pat. No. 5,704,461 discloses a rotational control apparatus, which relates specifically to fan clutches, having O-rings between relatively moveable components for sealing engagement to prevent fluid pressure from escaping. Standard elastomeric O-ring seals have proved inadequate for such purposes, in that their very exposure to such contaminants can result in deterioration of an O-ring seal in an accelerated manner, thereby leading to failure and the necessity for earlier replacement of the seal.
Seals with varying cross-sectional shapes such as xe2x80x9cS-shapedxe2x80x9d and xe2x80x9cU-shapedxe2x80x9d have been disclosed in U.S. Pat. Nos. 5,111,093; 5,257,682; and 6,003,876. In particular, U.S. Pat. No. 5,257,682 to Kuroki utilizes seals of various sizes and shapes in a hub clutch assembly for a vehicle which engages and disengages a drive axle relative to a wheel. The Kuroki patent shows a U-shaped seal configured such that the inner portion of the xe2x80x9cUxe2x80x9d envelopes a member, thereby creating an on/off valve in cooperation with an actuator that engages and disengages the seal. Although the Kuroki patent provides a seal capable of preventing pressure leakage from an actuator valve when the actuator is engaged with the seal, the Kuroki seal is not a permanent seal which limits exposure of a pressure chamber in a rotational control apparatus to moisture and other environmental contaminates.
The present invention is an annular seal disposed about a common axis between first and second rotatably opposed members. The seal is for sealing against ingress of foreign matter into a pressure chamber that is formed between the first and second members, wherein the first member has an annular extension and the second member has a radially extending surface. The seal comprises a center base section having a first side and a second side. A radially inner upright section extends generally perpendicularly from the first side of the center base section. The inner upright section has a first side, which generally faces the first side of the center base section and a second side, which generally faces away from the first side of the center base section. The seal also has a radially outer upright section extending from the first side of the center base section. The outer upright section is aligned at an acute angle relative to the center base section. The outer upright section has a first side, which generally faces the first side of the center base section and a second side, which generally faces away from the first side of the center base section. The first side of the center base section, the first side of the inner upright section and the first side of the outer upright section collectively form a generally U-shape in radial cross section. The second side of the center base section is in contact with the radially extending surface of the second member, while the first side of the center base section, the first side of the inner upright section and the first side of the outer upright section are in contact with the annular extension of the first member.